## Adaptation and Application of the CMAQ **Modeling System for Real**  **- time Air Quality**  **Forecasting During the Summer of 2004 R. Mathur, J. Pleim, T. Otte, K. Schere, J. Young, G. Pouliot, B. Eder**  Atmospheric Sciences Modeling Division, ARL/NOAA, NERL/U.S. EPA

**D. Kang, S. Yu, H. -**  **M. Lin** Science and Technology Corporation

**J. McQueen** National Centers for Environmental Prediction

**P. Lee, M. Tsidulko** Science Applications International Corporation

**D. Wong** Lockheed Martin Information Technology Although this work was reviewed by EP A and approved for publication, it may not necessarily reflect official Agency policy

# Eta - CMAQ AQF System

**Eta -**  **12 CMAQ**  **Eta Post PRDGEN**  **PREMAQ AQF Post**  **Ve rification T** 

**ools** Ve rtical interpolation from eta to sigma

Horizontal interpolation to Lambert grid CMAQ - ready meteorology and emissions Gridded ozone files for users Chemistry model Meteorology model Performance feedback for users and developers

# CMAQ Configuration • Structural
– Netcdf replaced with binary IOAPI 

## • Advection
– Horizontal: Piecewise Parabolic Method – Vertical: Upstream with rediagnosed vertical velocity to satisfy mass conservation 

## • Turbulent Mixing
– K-theory; PBL height from Eta – New scheme for specification of minimum Kz

# CMAQ Configuration **(contd.)** • Gas phase chemistry
– CB4 mechanism with EBI solver 

## • Cloud Processes
– Mixing and aqueous chemistry: following the scheme in RADM 

## • Deposition
– Dry : M3dry modified to use Eta land surface parameters – Wet 

## • Aerosols
– 2004 release version268 grid cells 259 grid cells **Northeast “1x”**  **Domain East “3x” Domain**  

## CMAQ **Modeling Domains**  Ozone forecasts on 3x and 1x Experimental PM forecasts on 3x

# Lateral Boundary Condition **Specification A key** **u ncertainty** **i n long term modeling**  **over limited area domains** 
– Determines “model background” 

## • Default profiles
– “Clean” tropospheric background values – Used in 1x 

## • Seasonal Profiles
– Derived from continental CMAQ simulations for 2001 – Used in 3x

# Lateral Boundary Conditions **(contd.)** • Ozone profiles from NCEP’s Global Forecast System (GFS)
– O 3 

### is a 3 - d prognostic variable – Initialized with Solar Backscatter Ultra -Violet (SBUV2) satellite observations

– Motivation • Simulating varying dynamical conditions • Improve model representation of O 3 

### in the free troposphere
– Effects associated with intrusions – Study FT - BL exchange mechanisms

# Specification **of Minimum K z**  

## • Minimum value of Kz 

## allowed to vary spatially depending on urban fraction ( f urban 

## ) • Kz = 0.1 m 2/s, f urban = 0 • Kz = 2.0 m 2/s, f urban = 1



### – allows min. Kz 

### in rural areas to fall off to lower values than urban regions during night-time; mimics urban heat island effects
– prevents precursor concentrations (e.g., CO, NOx) in urban areas from becoming too large at night
– lower Kz 

### (and reduced mixing intensity) in non - urban areas results in increased night-time O3 titration • Helps reduce night time over predictions of ozone “regionally”

### Summer 2004: **Aty pical Ozone Season**  **July 21 Au**  **g. 12**  Source: EP

A A IRNOW

### Model Performance Characteristics: Summer 2004Bias



## Ef fects of GFS Ozone and Cloud Mixing

O 3 Ve rtical profile Cloud top

# GFS Sensitivity Simulations • Limit GFS use to above a specified altitude – 6 km – 10 km • Motivation: to limit the use of GFS derived O 3 

### profiles to the upper levels of the model, where there is greatest confidence in GFS predictions and to avoid abnormally high O 3 

### within the boundary layer (noticed in early parts of May) 

## • Default BC (without GFS)

### Ta rget Day Stats: May 18, 2004

# Impact of GFS 6km and min. Kz 

# change **1x domain Solid**  **lines** -wi th changes **Dashed lines**  -wi thout changes Implemented in 1x domain on 7/20/04 Hourly 1 Hr. Max 8 Hr. Max

# Comparison **of 3x and 1x Performance**

At sites within the 1x domain

## Comparison **of 3x and 1x**

**Lateral Boundary Conditions**  Solid lines (3x); filled circles and dash line (1x) CMAQ 2001 Performance at 3x Western Boundary Solid lines: seasonal BCs Dash/dots: Default profile“Switch - Off” top - down cloud mixing

Tropopause limit on cloud top 

## Diagnostic **Te sts: Cloud**  **Mixing**

## Diagnostic **Te sts: Cloud**  **Mixing** Ta rget Day Stats: May 18, 2004
**FSIDE** : switch - of

f top - down mixing **TROPLIM** : tropopause limit on cloud top

## Diagnostic **Te sts: Cloud**  **effects on Photolysis**

O 3 (ppb) Cloud Fraction: Current (average) Cloud Fraction: Modified (max)**Scale by** 

**R adiation**  **reaching the surface**  **1 -**  **(J/Jclear)** 

### Photoly**sis Attenuation**  **Au gust**  **12, 2004**

## Effects of Cloud **Process Modifications**

**Maximum Reductions**  **in O 3**  

### August 12, 2004
Below cloud attenuation based on radiation Below cloud attenuation based on Radiation + switch - off top - down mixing+ New CFRAC

## Effects of Cloud **Process Modifications August 12, 2004**  **rad_atten** : cloud mixing + photolysis attenuation modifications

## Comparison **with Previous Day P**  **ersistence Max. 1 Hr** **. Ozone** Persistence Eta - CMAQ Correlation coefficient plots from S. McKeen

### PM **2.5** 

### Forecast Comparisons w **ith AIRNOW : Preliminary**  Daily Average August 15 August 16 August 17

# Summary • Lateral boundary conditions play a dominant role in regulating modeled O 3 

### background levels – Critical when ozone levels are relatively low as in the past two summers – Higher O 3 BC led to a systematic higher bias in the 3x simulation 

### • Careful consideration needs to be given in deriving LBCs from larger scale models – Are conditions representative? • Bias propagation – Consistent coupling 

### • Over- predictions at low O 3 

### range related to representation of cloud processes – Top - down mixing – Photolysis attenuation

# Looking **ahead ....** • Methods to improve coupling between models – Boundary conditions • GFS, Eta, CMAQ • Layer structure and model top to improve representation of tropopause dynamics • Comparison of model (GFS, CMAQ) and observed free tropospheric O 3 values 

### – Radiation • Photolysis attenuation 

### – Boundary layer mixing • Revisit Eta - K h 

### – Transition to WRF • Advection on E - grid – Minimize interpolations

# Looking **ahead ....** • Continue testing alternate formulations over a wider range of conditions
– Mixing – Below cloud washout (low observed O 3 during precipitation events) 

### • Assessment of experimental PM forecasts results
– Surface data: AIRNOW, IMPROVE, CASTNET – Satellites • AOD